Radiation-sensitive relief-forming materials having a suitable relief-forming material or photosensitive layer are known in the art. Important advances in the art and useful materials for making flexographic relief images are described in U.S. Patent Application Publication 2005/0227182 (Ali et al., hereinafter cited as US '182). This publication describes useful materials and methods for providing flexographic printing plates having a suitable relief image, using a thermally sensitive mask-forming imageable material to form a mask element.
Thus, a relief image can be produced by first creating a mask element, for example by thermally imaging a suitable masking film or mask element precursor to provide the desired pattern (generally using an infrared radiation laser under computer control) through which a photocurable or photosensitive material is imaged, typically using ultraviolet radiation. US '182 describes suitable mask element precursors, photosensitive materials, and process and apparatus for forming a mask element and eventual relief image.
Typically, a mask element can be placed in intimate contact with a photosensitive relief-forming precursor using a laminator device or vacuum drawdown, or both, and subjected to overall exposure with actinic radiation (for example, UV radiation) to cure the photosensitive composition in the relief-forming precursor in the unmasked areas, thus forming a negative image of the mask element in the photosensitive relief-forming precursor. The mask element can then be removed and the uncured regions on the relief-forming material can be removed using a development process. After drying, the resulting imaged relief-forming precursor has a relief image that can be used for flexographic or letterpress printing operations.
Advances in mask element precursors are described in U.S. Pat. No. 7,799,504 (Zwadlo et al.). Other useful mask element precursors and processes for their use are described in U.S. Pat. No. 8,198,012 (Zwadlo et al.) and U.S. Pat. No. 9,250,527 (Kidnie).
While the mask element precursors described in these publications have found considerable value in the flexographic industry, there is a need to further improve the process for making the mask elements in an efficient manner and to improve interlayer adhesion, intimate contact of mask element and relief-forming precursor during imaging when a lamination process is used, and a better draw-down of the mask element to the relief-forming precursor when vacuum draw-down is used.